This invention is directed to environmentally friendly solvents, and more particularly to cleaning, rinsing, and drying agents which are binary azeotropes or azeotrope-like compositions containing a volatile methyl siloxane (VMS).
Because state, federal, and international regulations are aimed at restricting the use of certain chemicals, the search for suitable replacements is a dilemma faced by domestic and foreign chemical and industrial sectors. Replacement of "outlawed" chemicals with volatile methyl siloxanes as solvent is a viable approach in America, because the Environmental Protection Agency (EPA) has determined that octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, hexamethyldisiloxane, octamethyltrisiloxane, and decamethyltetrasiloxane, are acceptable substitutes for chlorofluorocarbon C.sub.2 Cl.sub.3 F.sub.3 (CFC-113) and methylchloroform (MCF). This determination is limited to cleaning in closed systems in metal, electronics, and precision cleaning applications under EPA's Significant New Alternatives Policy (SNAP).
The EPA also exempted VMS as a volatile organic compound (VOC). VMS is in the list of compounds in 40 CFR 51.100(s) excluded from the definition of VOC on the basis that VMS compounds have negligible contribution to tropospheric ozone formation. Compounds in that list have negligible photochemical reactivity. The EPA noted that exempting VMS from regulation as ozone precursors could contribute to the achievement of several important environmental goals, in that VMS might be used as a substitute for several compounds that are listed as hazardous air pollutants (HAP). The EPA explained that this met the need to develop substitutes for ozone depleting substances (ODS); and that it would attain national ambient air quality standards for ozone under Title I of the Clean Air Act and the Federal implementation plan for Chicago's ozone non-attainment area. The designation VMS under the EPA exemption covers cyclic, branched, and linear "completely methylated" siloxanes, and means that methyl groups and no other functional groups are attached to the central backbone of the siloxane.
Volatile methyl siloxanes have an atmospheric lifetime of 10-30 days and do not contribute significantly to global warming. Volatile methyl siloxanes have no potential to deplete stratospheric ozone due to short atmospheric lifetimes so they do not rise and accumulate in the stratosphere. VMS contain no chlorine or bromine atoms; do not attack the ozone layer; do not contribute to tropospheric ozone formation (Smog); and have minimum GLOBAL WARMING potential. VMS are hence unique in simultaneously possessing these attributes.
It should therefore be apparent that VMS provide one positive solution to the problem of substituting new materials for "outlawed" chemicals as cleaning agents.